Injection molding is a process for fabrication of an article having the same shape as a molding cavity by feeding molten resin into the molding cavity in a certain form to fill the same and chilling the charged resin. According to recent advances in MEMS technology, a variety of different structures are now being fabricated using a stamp having a micropattern formed thereon.
In particular, such injection molding is generally used for mass-production of plastic articles and, since demand for plastic articles composed of high-strength polymers with excellent durability is noticeably increased with technical development over time, injection molding techniques are also currently utilized in a variety of applications.
In recent years, injection molding has been applied to production of plastic products used in aerospace, precision and/or optical instrument applications as well as general household plastic articles and, especially, may be used for some products requiring fine and precise patterns.
Briefly, in order to manufacture a plastic structure having a micropattern with a size of several nanometers to several micrometers formed on a surface of the structure, injection molding may be employed.
However, as to fabrication of a plastic article having a micropattern with a size of several nanometers to micrometers, an alternative stamper corresponding to the micropattern is duly used and such stamper is generally a plate type stamper.
Using the micropatterned stamper, shaped articles capable of embodying optical effects owing to constructive or destructive interference of light may be fabricated. For example, a micropattern have a nanometer scale line width is used, in turn being applicable to a high resolution spectrometer. Alternatively, a light diffusion promoting pattern may be formed, in turn being used as a backlight unit for an LCD.
Furthermore, by providing photonic band gap effects through regular alignment of ultra-fine patterns, light with a specific wavelength only may be reflected at the ultra-fine patterns while other wavelengths of light are transmitted and absorbed.
In general, in order to fabricate a stamper having such a micropattern or an ultra-fine pattern, a LIGA process (Lithographie, Galvanoformung, Abformung in German) is employed. FIG. 1 schematically illustrates a stamper fabrication process according to conventional technologies. Such a process includes: washing a silicon or glass substrate 10 and, after applying photoresist 20 to a surface of the substrate 10, soft baking the coating photoresist 20; placing a pattern mask with a desired pattern over the baked photoresist, exposing the same to light, developing the substrate through the exposed photoresist 20a, hard baking a part of the substrate on which the photoresist is partially removed from the substrate, in order to form the desired pattern; vacuum depositing any one of CrON, DLC (Diamond like carbon), C4F8, SAM (Self-assembled monolayer), etc. in order to form a seed layer 30; plating a metal such as Ni or Cu over the seed layer 30 to form a plated layer 50; and separating the plated layer 50 to form a stamper 50. Additional processes such as planarization of the stamper 50 and cutting of the planarized stamper may be further included, thereby manufacturing a master stamper.
However, in view of manufacturing time and cost, the foregoing method for fabrication of a stamper is not suited to fabrication of a stamper having a micrometer scale pattern (more than 1 μm), although it is useful for manufacturing a stamper with a nanoscale pattern (less than 1 μm) primarily because exposure and heat treatment require significantly high precision.
Even when LIGA is used to control a pitch and a height of the pattern, this method has disadvantages such as demand for high processing precision and high processing cost.
Moreover, it is difficult to fabricate a disk type stamper with a large area (such as a diameter of more than 4 inches) by LIGA and, when the area of the stamper is increased, manufacturing costs are dramatically increased.